Despite Friday's big rally, the price of oil slumped below $30 a barrel this week causing a steep drop in energy stocks. Companies with weak balance sheets were hit particularly hard, with a number of energy stocks plunging more than 30% this week. Leading the way, according to S&P Capital IQ data, were Chesapeake Energy (NYSE:CHK), NGL Energy Partners (NYSE:NGL), California Resources (NYSE:CRC), Unit Corp (NYSE:UNT), and Teekay Offshore Partners (NYSE:TOO).

Bankruptcy concerns were front and center this week and were a big reason why Chesapeake Energy and California Resources plunged. According to a report, Chesapeake Energy has hired attorneys to help it restructure, though that report was quickly shot down by the company. Meanwhile, concerns surrounding California Resources hefty debt load sent its stock spiraling lower after investors sold off its bonds.

The reason investors are worried about the survival of these companies is because the price of oil just keeps falling. That's what fueled Unit's slump this week, and added more fuel to the fire that incinerated the stocks of Chesapeake Energy and California Resources. All three companies need to see oil prices rally before investors will start buying their stocks.

Meanwhile, Teekay Offshore Partners and NGL Energy Partners slumped this week due to more company specific news. Teekay Offshore Partners had the contract for one of its vessels terminated early, while NGL Energy Partners reported weak earnings and watered down its guidance. Both companies are being affected by weaker oil prices, with Teekay Offshore Partners losing that contract because its customer was losing money pumping oil from an offshore oil field, while NGL Energy Partners was recovering less money from oil it collected from its water business.

To learn more about why these stocks moved so sharply, check out the following slideshow.

Matt DiLallo has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.